2013 Salmonella Outbreak Linked to Foster Farms Brand Chicken

Introduction

CDC collaborated with public health and agriculture officials in many states and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) to investigate a multistate outbreak of Salmonella Heidelberg infections. Epidemiologic, laboratory, and traceback investigations indicated that consumption of Foster Farms brand chicken was the source of this outbreak.

Public health investigators used the PulseNet system to identify cases of illness that were part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. PulseNet obtains DNA “fingerprints” of Salmonella bacteria through diagnostic testing and uses pulsed-field gel electrophoresis, or PFGE, to identify cases of illness.

Seven strains of Salmonella Heidelberg bacteria were identified as being linked to this outbreak. Before this outbreak, four of these strains were rarely reported to PulseNet. The other three strains were more common, with several ill persons infected with each strain reported to CDC monthly. Since some of these strains are more commonly reported to PulseNet, some illnesses may be part of the expected background and may not be linked to consumption of Foster Farms chicken. The DNA fingerprints of the Salmonella Heidelberg bacteria associated with this outbreak include the strain that was also associated with a multistate outbreak of Salmonella Heidelberg linked to Foster Farms brand chicken processed at an establishment in Washington during 2012-2013.

A total of 634 individuals infected with the outbreak strains of Salmonella Heidelberg were reported from 29 states and Puerto Rico from March 1, 2013 to July 11, 2014. Most of the ill persons (77%) were reported from California. The total number of ill persons identified in each state was as follows: Alaska (1), Alabama (1), Arkansas (1), Arizona (25), California (490), Colorado (9), Connecticut (1), Delaware (1), Florida (4), Georgia (1), Hawaii (1), Idaho (5), Illinois (4), Kentucky (1), Louisiana (1), Michigan (4), Missouri (5), Montana (1), Nevada (11), New Mexico (2), North Carolina (1), Oregon (17), Tennessee (1), Texas (13), Utah (6), Virginia (4), Washington (20), West Virginia (1), and Wisconsin (1); one illness was reported from Puerto Rico.

Among 633 persons for whom information was available, illness onset dates ranged from March 1, 2013 to July 11, 2014. Ill persons ranged in age from younger than 1 year to 93 years, with a median age of 18 years. Fifty percent of ill persons were male. Among 528 persons for whom information was available, 200 (38%) were hospitalized. Fifteen percent of ill persons developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths were reported.

The current outbreak appears to be over as the number of reported infections has returned to the expected number for this time of year. Since some of the outbreak strains are reported to PulseNet even in the absence of an outbreak, several ill persons infected with these strains are still expected to be reported to CDC monthly.

Epidemiologic Investigation

In interviews, ill persons answered questions about foods consumed and other exposures during the week before becoming ill. Two hundred and sixty (74%) of 350 ill persons interviewed reported consuming chicken prepared at home in the week before becoming ill. This proportion was significantly higher when compared with results from a survey of healthy persons [PDF – 29 pages] in which 65% reported consuming chicken prepared at home in the week before they were interviewed. Among those who had brand information available, 152 (87%) of 175 ill persons reported that they consumed Foster Farms brand chicken or another brand likely produced by Foster Farms.

Additionally, among the 490 ill persons reported in California, state and local health officials identified at least 25 ill persons as part of a cluster of illnesses in October 2013 during this outbreak. The ill persons consumed food purchased from the same Costco store location in South San Francisco in the week before they became sick. Based on interviews of ill persons, cooked rotisserie chicken purchased from this store location was linked to the illnesses. Shopper card information was successfully used to determine the specific food linked to illnesses and allowed investigators to identify the chicken involved as being supplied by Foster Farms. Ill persons gave permission for public health officials to retrieve purchase information based on shopper card numbers.

Laboratory Testing

During the outbreak investigation, health departments in California and Washington collected leftover chicken from the homes of ill persons for laboratory testing. Testing conducted by the Washington State Public Health Laboratories identified one of the outbreak strains of Salmonella Heidelberg in one unopened package of raw Foster Farms chicken collected from an ill person’s home in Washington. The unopened package did not contain information for the establishment in which the chicken was processed. Two samples of leftover rotisserie chicken were collected by California Department of Public Health from the homes of ill persons infected with outbreak strains of Salmonella Heidelberg identified during the cluster investigation in South San Francisco; laboratory testing conducted by the California Food and Drug Laboratory Branch identified one of the outbreak strains of Salmonella Heidelberg in both samples of leftover rotisserie chicken. Additional testing by California also identified one of the outbreak strains of Salmonella Heidelberg in sample of leftover raw Foster Farms chicken collected from an ill person’s home. The outbreak strain isolated from this person was different from the strain isolated from the leftover chicken sample.

Testing conducted by USDA-FSIS identified one of the outbreak strains of Salmonella Heidelberg in a sample of leftover raw Foster Farms chicken from an ill person’s home in California. The outbreak strain isolated from this person was different from the strain isolated from the leftover chicken sample.

The National Antimicrobial Resistance Monitoring System (NARMS) is a U.S. public health surveillance system that tracks antibiotic resistance in foodborne and other enteric bacteria found in people, raw meat and poultry, and food-producing animals. NARMS is an interagency partnership among CDC, the U.S. Food and Drug Administration (FDA), USDA, and state and local health departments.

The NARMS human surveillance program at CDC monitors antibiotic resistance in Salmonella and other bacteria isolated from clinical specimens submitted to NARMS by public health laboratories. CDC’s NARMS laboratory conducted antibiotic resistance testing on a total of 68 clinical isolates collected from ill persons infected with each of the seven outbreak strains of Salmonella Heidelberg. Of the 68 isolates tested, 24 (35%) were not resistant to any of the antibiotics tested by NARMS and 44 (65%) were drug resistant (defined as resistance to one or more antibiotics). Twenty-four (35%) of the 68 isolates were multidrug resistant (defined as resistance to one or more antibiotics in three or more drug classes). Not all drug-resistant isolates exhibited the same antibiotic resistance pattern. Isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Although these antibiotics are not typically used to treat Salmonella blood infections or other severe Salmonella infections, antibiotic resistance can be associated with increased risk of hospitalization in infected individuals.

Additionally, CDC’s NARMS laboratory received isolates from five chicken products produced by Foster Farms: four collected from ill people’s homes in California and Washington, and one collected from a warehouse chain store located in California.  Of the five isolates tested, one (20%) was not resistant to any of the antibiotics tested by NARMS and four (80%) were drug resistant. One (20%) of these five isolates was multidrug resistant. Not all drug-resistant isolates exhibited the same antibiotic resistance pattern. Isolates collected from chicken were resistant to combinations of the following antibiotics: kanamycin, streptomycin, sulfisoxazole, and tetracycline.

The NARMS retail meat and poultry surveillance program monitors antibiotic resistance in Salmonella and other bacteria isolated from raw retail meat and poultry. NARMS laboratorians isolated five of the seven outbreak strains from nine retail samples of Foster Farms chicken breasts and wings collected in California. Susceptibility testing was conducted on 8 of the 9 isolates; 8 out of 8 (100%) were drug resistant, and none (0%) were pansusceptible. Four out of the 8 (50%) isolates were multidrug resistant.  Not all isolates from poultry exhibited the same antibiotic resistance pattern. Isolates collected from poultry were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline.

Regulatory Investigation

During September 2013, FSIS conducted intensified in-facility testing for Salmonella at four Foster Farms production establishments in California and Washington. Six of the seven outbreak strains of Salmonella Heidelberg were isolated from raw chicken samples collected from the three Foster Farms establishments in California.

On October 7, 2013, USDA-FSIS issued a Public Health Alert due to concerns that illnesses caused by strains of Salmonella Heidelberg were associated with raw chicken products produced by Foster Farms at three facilities in California. On October 10, 2013, USDA-FSIS announced that Foster Farms submitted and implemented immediate substantive changes to their slaughter and processing to allow for continued operations.

On October 12 and October 17, 2013, a California warehouse store initiated recalls of Foster Farms rotisserie chicken products due to possible Salmonella Heidelberg contamination. USDA-FSIS, CDC, the California Department of Public Health, and the San Mateo Public Health Department determined through epidemiologic and traceback investigations that there was a link between the rotisserie chicken products and illness.

USDA-FSIS reinstated intensified sampling at the affected establishments following corrective actions in October 2013 and continues to monitor these establishments.  Since October 2013, there has been a steady decrease of Salmonella-positive samples in all three of the establishments after implementation of the corrective actions began.

On July 3, 2014, Foster Farms recalled an undetermined amount of chicken products that may be contaminated with a particular strain of Salmonella Heidelberg. The recall resulted from USDA-FSIS identifying one of the outbreak strains of Salmonella Heidelberg in an intact sample of Foster Farms brand chicken collected from the home of a person in California infected with the same strain. The chicken breasts were packaged with critical labeling information to associate the product with the establishment and a specific production date.  The ill person’s family purchased their chicken in March; however, it was stored in the family’s freezer and some of it was consumed in late April.

Foster Farms has implemented and continues to utilize multiple interventions to reduce Salmonella throughout its entire poultry production process. This strategy includes interventions at the breeder level, at hatcheries, at grow-out farms, and at the processing plant where the final product is packaged.  Supported by data from continuous testing by Foster Farms, these interventions have reduced Salmonella prevalence to less than 5 percent in the Foster Farms establishments linked to this outbreak.

FSIS has determined that process control measures undertaken by the firm to consistently minimize Salmonella contamination of raw chicken have been successful.  

Final Case Count Update

A total of 634 individuals infected with the outbreak strains of Salmonella Heidelberg were reported from 29 states and Puerto Rico from March 1, 2013 to July 11, 2014. Most of the ill persons (77%) were reported from California. Since the last update on July 4, 2014, a total of 13 additional ill persons were reported from 2 states: California (10) and Illinois (3).

Among 633 persons for whom information was available, illness onset dates ranged from March 1, 2013 to July 11, 2014. Ill persons ranged in age from younger than 1 year to 93 years, with a median age of 18 years. Fifty percent of ill persons were male. Among 528 persons with available information, 200 (38%) reported being hospitalized. Fifteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

The current outbreak appears to be over as the number of reported infections has returned to the expected number for this time of year. Since some of the outbreak strains are reported to PulseNet even in the absence of an outbreak, several ill persons infected with these strains are still expected to be reported to CDC monthly.

Case Count Update

As of July 2, 2014, a total of 621 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 29 states and Puerto Rico since March 1, 2013. Most of the ill persons (77%) have been reported from California. Since the last update on May 27, 2014, a total of 47 additional ill persons have been reported from 5 states: Alabama (1), California (39), Oregon (3), Washington (3), and West Virginia (1). Fifteen (32%) of these additional ill persons have illness onset dates in June. During this time of year, approximately 3 to 5 illnesses with the outbreak strains would be expected each week; recently, 6 to 9 illnesses have occurred each week.

Among 608 persons for whom information is available, illness onset dates range from March 1, 2013 to June 15, 2014. Ill persons range in age from younger than 1 year to 93 years, with a median age of 18 years. Fifty percent of ill persons are male. Among 504 persons with available information, 181 (36%) reported being hospitalized. Thirteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

This outbreak investigation is ongoing; however, since an increase in illnesses noted in February and March, there has been a decline in the weekly number of illnesses occurring. The number of illnesses is now approaching the expected number for this time of year.  Illnesses that began after June 2, 2014, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

On July 3, 2014, Foster Farms recalled an undetermined amount of chicken products that may be contaminated with a particular strain of Salmonella Heidelberg. The recall resulted from USDA-FSIS identifying one of the outbreak strains of Salmonella Heidelberg in an intact sample of Foster Farms brand chicken collected from the home of a person infected with the same strain in California. The chicken breasts were packaged with critical labeling information to associate the product with the establishment and a specific production date. The ill person’s family purchased their chicken in March; however, it was stored in the family’s freezer and consumed in late April. Although the recalled chicken has production dates of March 7 through March 13, 2014, USDA-FSIS and CDC are concerned that the recalled chicken could still be in people’s freezers. Consumers should check their freezers for the recalled chicken and should not eat it.

Case Count Update

As of May 22, 2014, a total of 574 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 27 states and Puerto Rico since March 1, 2013. Most of the ill persons (77%) have been reported from California. Since the last update on April 9, 2014, a total of 50 new ill persons have been reported from 8 states: Arizona (1), California (42), Georgia (1), Montana (1), Nevada (1), Oregon (1), Texas (1), and Utah (2). Since the last update, an average of 8 new ill persons have been reported each week to CDC.

Among 560 persons for whom information is available, illness onset dates range from March 1, 2013 to May 1, 2014. Ill persons range in age from less than 1 year to 93 years, with a median age of 18 years. Fifty-one percent of ill persons are male. Among 478 persons with available information, 178 (37%) reported being hospitalized. Thirteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that began after April 22, 2014, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Case Count Update

As of April 7, 2014, a total of 524 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 25 states and Puerto Rico since March 1, 2013. Most of the ill persons (76%) have been reported from California. Since the last update on March 3, 2014, a total of 43 new ill persons have been reported from 5 states: Arizona (2), California (34), Michigan (1), Oregon (3), Texas (2), and Washington (1).

Among 518 persons for whom information is available, illness onset dates range from March 1, 2013 to March 18, 2014. Ill persons range in age from less than 1 year to 93 years, with a median age of 18 years. Fifty-one percent of ill persons are male. Among 437 persons with available information, 162 (37%) reported being hospitalized. Thirteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that began after March 8, 2014, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

In interviews, ill persons answered questions about foods consumed and other exposures during the week before becoming ill. Three hundred and ten (86%) of 361 ill persons interviewed to date report consuming chicken in the week before becoming ill. Among those who had brand information available, 119 (74%) of 161 ill persons reported that they had consumed Foster Farms brand chicken or another brand likely produced by Foster Farms.

CDC and state and local public health partners continue to focus the investigation on interviewing ill persons about foods eaten and other exposures before becoming ill, continuing laboratory surveillance through PulseNet to identify additional ill persons who have infections with outbreak-associated strains, and testing recent outbreak strains for antibiotic resistance. CDC is working closely with USDA-FSIS which is assessing interventions implemented at Foster Farms facilities to prevent future illnesses.

CDC’s NARMS laboratory continues to conduct antimicrobial susceptibility testing on clinical isolates collected from ill persons infected with any of the seven outbreak strains. Of 61 isolates tested to date, 38 (62%) exhibited resistance to one or more antibiotics. Nineteen (31%) of the 61 isolates were multidrug resistant. To date, isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Although these antibiotics are not typically used to treat Salmonella bloodstream infections or other severe Salmonella infections, antibiotic resistance can be associated with a higher risk of hospitalization in infected individuals. Isolates collected from ill persons reported in 2014 have exhibited similar patterns of antibiotic resistance as isolates collected from ill persons reported in 2013.

Case Count Update

This outbreak investigation continues. Previously, the outbreak appeared to be over, but recent findings indicate otherwise. The number of reported infections from all seven outbreak strains of Salmonella Heidelberg returned to baseline levels in January and the outbreak appeared to be over, as noted in the previous update on January 16, 2014. However, the investigation continued and ongoing surveillance in February identified that infections from two of the previously rare outbreak strains have again exceeded the number of infections expected to be reported to PulseNet during this time of year.

As of February 28, 2014, a total of 481 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 25 states and Puerto Rico since March 1, 2013. Most of the ill persons (76%) have been reported from California.

Since the last update on January 16, 2014, a total of 51 new ill persons have been reported from 5 states: Arizona (3), California (44), Hawaii (1), Tennessee (1), and Utah (2). CDC and state and local public health partners are focusing the investigation on interviewing ill persons about foods eaten and other exposures before becoming ill, continuing laboratory surveillance through PulseNet to identify additional ill persons who have infections with outbreak-associated strains, and testing recent outbreak strains for antibiotic resistance.

Information about illnesses is available from 472 persons.  The dates the illnesses began range from March 1, 2013 to February 11, 2014. Ill persons range in age from less than 1 year to 93 years, with a median age of 18 years. Fifty-one percent of ill persons are male. Among 394 persons with available information, 151 (38%) reported being hospitalized. Thirteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that began after January 29, 2014, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

The NARMS retail meat surveillance program isolated one of the two outbreak strains of Salmonella Heidelberg that has recently increased from a retail sample collected in California of Foster Farms brand chicken wings, purchased on January 27, 2014.

Testing conducted by USDA-FSIS identified the other outbreak strain of Salmonella Heidelberg that has recently increased in a leftover sample of raw chicken from an ill person’s home in California. The person became ill on January 11, 2014. The outbreak strain isolated from this person was different from the strain isolated from the leftover chicken sample. Using shopper card records obtained with permission from the ill person, investigators determined that the chicken was a brand likely produced by Foster Farms. However, no packaging was available with the tested product to confirm this and the production date of this sample is unknown.

Antibiotic resistance testing results are not yet available for isolates from recent ill persons or isolates from recent food samples. Results of this testing will be reported when they become available.

Case Count Update

As of January 15, 2014, a total of 430 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 23 states and Puerto Rico. Most of the ill persons (74%) have been reported from California. Since the last update on December 19, 2013, a total of 14 new ill persons have been reported from four states: Arizona (1), California (11), Idaho (1), and Virginia (1).

Among 418 persons for whom information is available, illness onset dates range from March 1, 2013 to December 26, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 18 years. Fifty-two percent of ill persons are male. Among 359 persons with available information, 137 (38%) reported being hospitalized. Thirteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

The number of reported infections from the outbreak strains of Salmonella Heidelberg has returned to baseline levels indicating that this particular outbreak appears to be over. However, activities related to this investigation are ongoing. Illnesses that occurred after December 15, 2013, might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

CDC’s NARMS laboratory continues to conduct antimicrobial susceptibility testing on clinical isolates collected from ill persons infected with any of the seven outbreak strains. Of 54 isolates tested to date, 32 (59%) exhibited resistance to one or more antibiotics. Fifteen (28%) of the 54 isolates were multidrug resistant. To date, isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Although these antibiotics are not typically used to treat Salmonella bloodstream infections or other severe Salmonella infections, antibiotic resistance can increase the risk of hospitalization in infected individuals.

Additionally, CDC’s NARMS laboratory received isolates from five chicken products produced by Foster Farms: four collected from ill people’s homes in California and Washington and one collected from a warehouse chain store located in California. Of the five isolates tested, four (80%) exhibited resistance to one or more antibiotics. One isolate (20%) was multidrug resistant. Isolates collected from chicken were resistant to combinations of the following antibiotics: gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline.

Case Count Update

As of December 18, 2013, a total of 416 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 23 states and Puerto Rico. Most of the ill persons (74%) have been reported from California. Since the last update on November 19, 2013, a total of 27 new ill persons have been reported from 4 states: Arizona (2), California (22), Colorado (2), and Washington (1).

Among 403 persons for whom information is available, illness onset dates range from March 1, 2013 to December 1, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 19 years. Fifty-one percent of ill persons are male. Among 340 persons with available information, 134 (39%) reported being hospitalized. Thirteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that occurred after November 17, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

CDC’s NARMS laboratory continues to conduct antimicrobial susceptibility testing on clinical isolates collected from ill persons infected with all seven of the outbreak strains. Of 34 isolates tested to date, 19 (56%) of these isolates exhibited resistance to one or more antibiotics. Seven (21%) of the 34 isolates were multidrug resistant. To date, isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Antibiotic resistance may increase the risk of hospitalization or possible treatment failure in infected individuals.

Seven strains of Salmonella Heidelberg bacteria have been identified as being linked to this outbreak. Ill persons infected with each of the seven strains were linked to consumption Foster Farms chicken. Four of these strains are rarely reported to PulseNet. The other three strains are more common, with several ill persons infected with each strain reported to CDC monthly. The number of reported cases for these three strains was significantly higher than the number of cases expected during the outbreak period. Since illnesses due to several strains are more commonly reported, not all may be linked to consumption of Foster Farms chicken and may be part of the expected number of illnesses reported during this period.

Case Count Update

As of November 15, 2013, a total of 389 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 23 states and Puerto Rico. Most of the ill persons (74%) have been reported from California. Since the last update on October 30, 2013, 28 new ill persons have been reported from 8 states: Arizona (2), California (20), Idaho (1), Illinois (1), Louisiana (1), Nevada (1), Oregon (1), and Virginia (1). One ill person from Texas has been removed from the CDC case count because the person does not meet the outbreak case definition.

Among 380 persons for whom information is available, illness onset dates range from March 1, 2013 to October 29, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 19 years. Fifty-two percent of ill persons are male. Among 312 persons with available information, 125 (40%) reported being hospitalized. Fourteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that occurred after October 14, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Case Count Update

As of October 29, 2013, a total of 362 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 21 states and Puerto Rico. Most of the ill persons (74%) have been reported from California. Since the last update on October 18, 2013, 24 new ill persons have been reported from six states: California (16), Colorado (3), Delaware (1), Idaho (1), Michigan (1), and Texas (2).

Among 356 persons for whom information is available, illness onset dates range from March 1, 2013 to October 8, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 19 years. Fifty-two percent of ill persons are male. Among 259 persons with available information, 98 (38%) reported being hospitalized. Fourteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that occurred after September 28, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks

Case Count Update

As of October 17, 2013, a total of 338 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 20 states and Puerto Rico. Most of the ill persons (75%) have been reported from California. Since the last update on October 11, 2013, 22 new ill persons have been reported from three states: Arizona (1), California (20), and Oregon (1).

Among 331 persons for whom information is available, illness onset dates range from March 1, 2013 to October 2, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 18 years. Fifty-two percent of ill persons are male. Among 234 persons with available information, 93 (40%) reported being hospitalized. Fourteen percent of ill persons have developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that occurred after September 17, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

Among the 252 ill persons reported in California, state and local health officials identified at least 25 ill persons as part of a cluster of illness. The ill persons consumed food purchased from the same Costco store location in South San Francisco in the week before they became sick. Based on interviews of ill persons, an association was identified between illness and consumption of cooked rotisserie chicken purchased from this store location. Shopper card information was successfully used to determine the specific food linked to illnesses and allowed investigators to identify the chicken involved as belonging to the Foster Farms brand. Ill persons gave permission for public health officials to retrieve purchase information based on shopper card numbers. This investigation is ongoing.

Two samples of leftover rotisserie chicken were collected by public health officials from the home of ill persons in California infected with outbreak strains of Salmonella Heidelberg. Laboratory testing conducted by the California Food and Drug Laboratory Branch identified one of the outbreak strains of Salmonella Heidelberg in both samples of leftover rotisserie chicken.

On October 12, 2013, Costco’s El Camino Real store located in South San Francisco, California recalled more than 9,000 units (approximately 40,000 pounds) of rotisserie chicken products. The products subject to recall included 8,730 “Kirkland Signature Foster Farms” rotisserie chickens and 313 total units of “Kirkland Farm” rotisserie chicken soup, rotisserie chicken leg quarters, and rotisserie chicken salad.  The products were sold directly to consumers in the Costco store between September 11, 2013 and September 23, 2013. While the use-by date has passed and these products are no longer available for retail sale, USDA-FSIS is concerned that some product may be frozen in consumers’ freezers.

On October 17, 2013, Costco’s El Camino Real store recalled an additional 14,093 units of rotisserie chicken products that may be contaminated with Salmonella Heidelberg. This is in addition to the 9,043 units that were recalled on October 12, 2013. The products subject to recall include 13,455 “Kirkland Signature Foster Farms” rotisserie chickens and 638 total units of “Kirkland Farm” rotisserie chicken soup, rotisserie chicken leg quarters, and rotisserie chicken salad. The products were sold directly to consumers in the Costco store between September 24, 2013 and October 15, 2013. Costco and the California Department of Public Health discovered through a follow-up investigation to the previous recall that additional product should be recalled. No illnesses have been reported in association with the product recalled on October 17, 2013.  According to USDA-FSIS, the problem with possibly contaminated rotisserie chicken products at this Costco location may be the result of cross-contamination after the cooking process in the preparation area.

Seven strains of Salmonella Heidelberg bacteria have been identified as being linked to this outbreak. Ill persons infected with each of the seven strains were linked to consumption Foster Farms chicken. Four of these strains are rarely reported to PulseNet. The other three strains are more common, with several ill persons infected with each strain reported to CDC monthly. Since illnesses due to several strains are more commonly reported, not all may be linked to consumption of Foster Farms chicken and may be part of the expected number of illnesses reported during this period.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview them about foods eaten before becoming ill. USDA-FSIS is continuing to work closely with CDC and state partners during this investigation.

Case Count Update

As of October 11, 2013, a total of 317 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 20 states and Puerto Rico. Most of the ill persons (73%) have been reported from California. Since the last update on October 8, 2013, a total of 39 additional ill persons have been identified from 9 states and Puerto Rico: Arizona (2), California (19), Florida (2), Kentucky (1), Missouri (5), Nevada (1), New Mexico (2), Puerto Rico (1), Texas (4), and Virginia (2). Of the 39 additional ill persons, two have estimated illness onset dates after September 24, 2013, the last illness onset date reported in the October 8, 2013 outbreak announcement. Since the last update, one ill person originally reported from Hawaii was found to be a resident of Florida. This person is now included in the Florida case count.

Among 310 persons for whom information is available, illness onset dates range from March 1, 2013 to September 26, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 20 years. Fifty-one percent of ill persons are male. Among 189 persons with available information, 79 (42%) reported being hospitalized. Thirteen percent of ill persons developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.

Illnesses that occurred after September 5, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks.

Investigation Update

To date, seven strains of Salmonella Heidelberg have been included in this investigation based on epidemiologic, laboratory and traceback information. The information collected for cases associated with each strain indicates that each of the strains is linked to this outbreak of multidrug-resistant Salmonella Heidelberg infections and that Foster Farms brand chicken is the likely source.

CDC’s NARMS laboratory conducted antibiotic-resistance testing on clinical isolates collected from ten ill persons infected with three of the seven outbreak strains. Nine of these isolates exhibited drug resistance to one or more commonly prescribed antibiotics. Of those, three were multidrug resistant. One isolate was susceptible to all antibiotics tested. To date, isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Antimicrobial resistance may increase the risk of hospitalization or possible treatment failure in infected individuals.

On October 10, 2013, USDA-FSIS announced that Foster Farms submitted and implemented immediate substantive changes to their slaughter and processing to allow for continued operations. FSIS inspectors will verify that these changes are being implemented on a continuous and ongoing basis. Additionally, the agency will continue intensified sampling and testing of chicken products from these facilities for at least the next 90 days.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview them about foods eaten before becoming ill. USDA-FSIS is continuing to work closely with CDC and state partners during this investigation.

Initial Announcement

CDC is collaborating with public health and agriculture officials in many states and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) to investigate a multistate outbreak of Salmonella Heidelberg infections. Public health investigators are using DNA “fingerprints” of Salmonella bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that may be part of this outbreak. They are using data from PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections. Seven strains of Salmonella Heidelberg bacteria have been identified as being linked to this outbreak. Four of these strains are rarely reported to PulseNet. The other three strains are more common, with several ill persons infected with each strain reported to CDC monthly. The DNA fingerprints of the Salmonella Heidelberg bacteria associated with the current outbreak include the strain that was also associated with a multistate outbreak of Salmonella Heidelberg linked to Foster Farms brand chicken during 2012-2013.

As of October 7, 2013, a total of 278 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 17 states. Most of the ill persons (77%) have been reported from California. The number of ill persons identified in each state is as follows: Alaska (2), Arkansas (1), Arizona (11), California (213), Colorado (4), Connecticut (1), Florida (1), Hawaii (1), Idaho (2), Michigan (2), North Carolina (1), Nevada (8), Oregon (8), Texas (5), Utah (2), Washington (15) and Wisconsin (1).

Among 274 persons for whom information is available, illness onset dates range from March 1 to September 24, 2013. Ill persons range in age from <1 year to 93 years, with a median age of 20 years. Fifty-one percent of ill persons are male. Among 183 persons with available information, 76 (42%) reported being hospitalized. No deaths have been reported.

The outbreak can be visually described with a chart showing the number of people who became ill each day or week. This chart is called an epi curve. Illnesses that occurred after September 1, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks. For more details, please see Salmonella Outbreak Investigations: Timeline for Reporting Cases.

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicate that consumption of Foster Farms brand chicken is the likely source of this outbreak of Salmonella Heidelberg infections.

In interviews, ill persons answered questions about foods consumed and other exposures during the week before becoming ill. One hundred and five (80%) of 132 ill persons interviewed report consuming chicken prepared at home in the week before becoming ill. This proportion is significantly higher when compared with results from a survey of healthy persons [PDF – 29 pages] in which 65% reported consuming chicken prepared at home in the week before they were interviewed. Among those who had brand information available, 48 (79%) of 61 ill persons reported that they had consumed Foster Farms brand chicken or another brand likely produced by Foster Farms.

The National Antimicrobial Resistance Monitoring System (NARMS) retail meat surveillance program is an ongoing collaboration among the U.S. Food and Drug Administration’s Center for Veterinary Medicine, CDC, and participating state public health laboratories. NARMS monitors antibiotic resistance in Salmonella, Campylobacter, Enterococcus, and Escherichia coli bacteria isolated from raw retail meats. NARMS laboratorians isolated four of the seven outbreak strains from five retail samples of Foster Farms chicken breasts and wings collected in California. Four of these isolates exhibited drug resistance to one or more commonly prescribed antibiotics. Of these, two were multidrug resistant (defined as resistance to three or more classes of antibiotics). Not all isolates from poultry exhibited the same antibiotic-resistance pattern. To date, isolates collected from poultry were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline.

Additionally, CDC’s NARMS laboratory conducted antibiotic-resistance testing on clinical isolates collected from five ill persons infected with two of the seven outbreak strains. Four of these isolates exhibited drug resistance to one or more commonly prescribed antibiotics. Of those, two were multidrug resistant. One isolate was susceptible to all antibiotics tested. To date, isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Antimicrobial resistance may increase the risk of hospitalization or possible treatment failure in infected individuals.

Testing conducted by the Washington State Public Health Laboratories identified one of the outbreak strains of Salmonella Heidelberg in one leftover intact sample of raw Foster Farms chicken collected from an ill person’s home in Washington.

Preliminary laboratory testing identified four of the seven outbreak strains from multiple chicken product samples at three Foster Farms facilities; additional analysis is ongoing. USDA-FSIS has issued a Public Health Alert due to concerns that illnesses caused by strains of Salmonella Heidelberg are associated with raw chicken products produced by Foster Farms at three facilities in California. At this point in the investigation, FSIS is unable to link the illnesses to a specific product and a specific production period. The products were mainly distributed to retail outlets in California, Oregon and Washington State. Raw products from the facilities in question bear one of the establishment numbers inside a USDA mark of inspection or elsewhere on the package “P6137,” “P6137A,” and “P7632.”

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview about foods eaten before becoming ill. USDA-FSIS is continuing to work closely with CDC and state partners during this investigation.